Many electronic devices are powered by a battery. Those battery powered electronic devices that minimize power consumption and conserve battery power have a commercial advantage as they help extend the operating time of the electronic device. Accordingly, a significant amount of money and effort has been expended to reduce the amount of energy consumed by battery powered devices.
Radiotelephones are one type of battery powered electronic device. Radiotelephones, such as those operating in accordance with the time division multiple access (TDMA) standard, employ two modes of operation: a control mode and a communication mode. In an active state of the control mode, the radiotelephone intermittently receives paging information from a remote device while waiting to either place or receive a phone call and enter the communication mode. When the radiotelephone is not receiving paging information in the control mode (i.e., is idle), it enters a standby state in which portions of the radiotelephone are placed in a powered-off state to reduce power consumption.
One portion of a radiotelephone that is typically not placed in a powered-off state is the master clock. The master clock provides a high speed timing reference used by a controller in a radiotelephone to communicate programming over a high capacity bus to other integrated circuits in the radiotelephone. Placing the master clock in a powered-off state disables such programming and, in practicality, disables the radiotelephone. When the master clock is off, the controller can not communicate programming to the other integrated circuits to, for example, return to a powered-on state when exiting the standby state.
On the other hand, one skilled in the art will recognize that the master clock is a significant source of power consumption. For example, a system clock running at 13 MHz can draw as much as 1 mA of current during each idle period when no paging information is being received. Therefore, to maximize reduction of power consumption, what is needed is an apparatus for, and method of, communication control in an electronic device that permits periodical powering off of circuitry, such as the master clock.